Brian T posted a cryptic crossword clue recently, and Amy H posted the answer but used rot13 to avoid spoiling it for everyone else who might be trying to figure it out.

I thought that was a clever approach. So when Brian posted another clue and I figured out the answer, I decided to post it in rot13 form.

The answer to the clue was the word robe.

If you rot13 robe, you get ebor. Which is robe backwards. Which makes rot13 not a very effective way to conceal the word.

I mentioned this, and Brian came up with the term triskaidekadrome to describe a word which is the same rot13ed as reversed.

And it occurred to me that, given a text file containing a dictionary's worth of words (like the file that in most UNIX systems lives at /usr/dict/words or /usr/share/dict/words), it would be easy to automatically compile a list of all triskaidekadromes.

So I did.

Here's the resulting list, from Webster's Second International, 1934. However, most of the words here aren't in MW3 Unabridged, and some also aren't in Wikipedia and don't have relevant web-search results, which makes me wonder what they were doing in Webster's Second. But maybe they've just fallen out of use in the past 75+ years.

  • an
  • anan (variant of anon)
  • averin (not in MW3. Wikipedia says it's a protein that's like gluten, but I'm not seeing any reliable sources for that)
  • bo (presumably as in “bo tree,” or maybe “bo staff”?)
  • bobo (the only non-proper-noun use I'm finding is a portmanteau for “bourgeois bohemian,” coined in 2000)
  • er
  • gant (French for glove)
  • gnat
  • grivet (a species of monkey)
  • Hu (has various meanings, all proper nouns, unless you count the Chinese word for butterfly)
  • ly (a letter in the Hungarian alphabet, or a suffix or prefix, or various proper nouns)
  • Na (various proper nouns)
  • nana
  • Rane (various proper nouns)
  • ravine
  • re
  • rebore
  • rive
  • robe
  • serf
  • tang
  • thug
  • veri (a couple of proper nouns)

My favorite from that list is ravine. I rather like grivet, too, but not quite as much, just 'cause I had never heard it before.

In case anyone's interested, here's the Perl code I wrote. Should run on most systems, but you may have to change the path to perl in the first line, and/or the path to the words file in the open line.

use strict;
use warnings;

open(my $WORDFILE, "<", "/usr/share/dict/web2");

while (my $text = <$WORDFILE>)
 chop $text;
 $text = lc $text;
 $text =~ s/[- ]//g;
 my $rot13 = $text;
 $rot13 =~ tr[a-z][n-za-m];
 my $reversed = reverse $text;
 if ($rot13 eq reverse $text)
   print $text . "\n";

The line that removes hyphens and spaces isn't strictly necessary for this particular word file; I included that so I could also search the other word file on my computer, which contains hyphenated terms and phrases containing spaces. Sadly, searching that file turned up no triskaidekadromes.